SUMMARY This revised application is for a Phase I SBIR grant under PA-17-302 in which NIAID and DAIDS have expressed a special emphasis on the ?development of anti-HIV agents directed at new viral or cellular targets for treatment of HIV infection.? The goal of our proposal is to address the call to evaluate novel drug targets by conducting preclinical studies for a first-in- class antiretroviral (ARV) therapeutic for which we have obtained a strong foundation for mechanism of action (MOA) through lead development of an HIV-1 (HIV) Vif antagonist. The compounds described herein enable the host cell factors APOBEC3G (A3G) and APOBEC3F (A3F) involved in innate immunity to broadly neutralize HIV through APOBEC-dependent hypermutation of viral genomes during reverse transcription. We have conducted medicinal chemistry to optimize leads with increased efficacy in the single-digit nanomolar range against HIV isolates from clades A, B and C. Since the initial submission of this proposal we also have comprised a prodrug strategy to increase plasma half-life in vivo and chemical synthesis for both the lead, SN38-L and prodrug, Irino-L, have been optimized. Moreover, ADMET studies revealed promising parameters and have addressed the initial reviewers? concerns of toxicity. Based on reviewer recommendations this SBIR proposal now seeks to prioritize detailed pharmacokinetic (PK) studies, humanized mice in vivo efficacy studies, and viral resistance studies. As requested by the reviewers, studies required by the FDA under the ?Guidance for Industry Antiviral Product Development: Conducting and Submitting Virology Studies to the Agency? have been moved to Phase II.